package com.dyy.tsp.common.security;

import javax.crypto.Cipher;
import java.io.ByteArrayOutputStream;
import java.security.*;
import java.security.interfaces.RSAPrivateKey;
import java.security.interfaces.RSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
* <p>
* RSA公钥/私钥/签名工具包
* </p>
* <p>
* 字符串格式的密钥在未在特殊说明情况下都为BASE64编码格式<br/>
* 由于非对称加密速度极其缓慢，一般文件不使用它来加密而是使用对称加密，<br/>
* 非对称加密算法可以用来对对称加密的密钥加密，这样保证密钥的安全也就保证了数据的安全
* </p>
* @author yangyang
*/
@SuppressWarnings("all")
public class RSA_PKCS8Util {

    /**
     * 加密算法RSA
     */
   public static final String KEY_ALGORITHM = "RSA";

    /**
     * 签名算法
     */
   public static final String SIGNATURE_ALGORITHM = "MD5withRSA";

    /**
     * 获取公钥的key
     */
   private static final String PUBLIC_KEY = "RSAPublicKey";

    /**
     * 获取私钥的key
     */
   private static final String PRIVATE_KEY = "RSAPrivateKey";

    /**
     * RSA最大加密明文大小
     */
   private static final int MAX_ENCRYPT_BLOCK = 117;

    /**
     * RSA最大解密密文大小
     */
   private static final int MAX_DECRYPT_BLOCK = 128;

   /** *//**
    * <p>
    * 生成密钥对(公钥和私钥)
    * </p>
    *
    * @return
    * @throws Exception
    */
   public static Map<String, Object> genKeyPair() throws Exception {
       KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
       keyPairGen.initialize(1024);
       KeyPair keyPair = keyPairGen.generateKeyPair();
       RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();
       RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();
       Map<String, Object> keyMap = new HashMap<String, Object>(2);
       keyMap.put(PUBLIC_KEY, publicKey);
       keyMap.put(PRIVATE_KEY, privateKey);
       return keyMap;
   }

   /** *//**
    * <p>
    * 用私钥对信息生成数字签名
    * </p>
    *
    * @param data 已加密数据
    * @param privateKey 私钥(BASE64编码)
    *
    * @return
    * @throws Exception
    */
   public static String sign(byte[] data, String privateKey) throws Exception {
       byte[] keyBytes = Base64Util.decode(privateKey);
       PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
       KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
       PrivateKey privateK = keyFactory.generatePrivate(pkcs8KeySpec);
       Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
       signature.initSign(privateK);
       signature.update(data);
       return Base64Util.encode(signature.sign());
   }

   /** *//**
    * <p>
    * 校验数字签名
    * </p>
    *
    * @param data 已加密数据
    * @param publicKey 公钥(BASE64编码)
    * @param sign 数字签名
    *
    * @return
    * @throws Exception
    *
    */
   public static boolean verify(byte[] data, String publicKey, String sign)
           throws Exception {
       byte[] keyBytes = Base64Util.decode(publicKey);
       X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);
       KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
       PublicKey publicK = keyFactory.generatePublic(keySpec);
       Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
       signature.initVerify(publicK);
       signature.update(data);
       return signature.verify(Base64Util.decode(sign));
   }

   /** *//**
    * <P>
    * 私钥解密
    * </p>
    *
    * @param encryptedData 已加密数据
    * @param privateKey 私钥(BASE64编码)
    * @return
    * @throws Exception
    */
   public static byte[] decryptByPrivateKey(byte[] encryptedData, String privateKey)
           throws Exception {
       byte[] keyBytes = Base64Util.decode(privateKey);
       PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
       KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
       Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
       Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
       cipher.init(Cipher.DECRYPT_MODE, privateK);
       int inputLen = encryptedData.length;
       ByteArrayOutputStream out = new ByteArrayOutputStream();
       int offSet = 0;
       byte[] cache;
       int i = 0;
       // 对数据分段解密
       while (inputLen - offSet > 0) {
           if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
               cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
           } else {
               cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
           }
           out.write(cache, 0, cache.length);
           i++;
           offSet = i * MAX_DECRYPT_BLOCK;
       }
       byte[] decryptedData = out.toByteArray();
       out.close();
       return decryptedData;
   }

   /** *//**
    * <p>
    * 公钥解密
    * </p>
    *
    * @param encryptedData 已加密数据
    * @param publicKey 公钥(BASE64编码)
    * @return
    * @throws Exception
    */
   public static byte[] decryptByPublicKey(byte[] encryptedData, String publicKey)
           throws Exception {
       byte[] keyBytes = Base64Util.decode(publicKey);
       X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
       KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
       Key publicK = keyFactory.generatePublic(x509KeySpec);
       Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
       cipher.init(Cipher.DECRYPT_MODE, publicK);
       int inputLen = encryptedData.length;
       ByteArrayOutputStream out = new ByteArrayOutputStream();
       int offSet = 0;
       byte[] cache;
       int i = 0;
       // 对数据分段解密
       while (inputLen - offSet > 0) {
           if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
               cache = cipher.doFinal(encryptedData, offSet, MAX_DECRYPT_BLOCK);
           } else {
               cache = cipher.doFinal(encryptedData, offSet, inputLen - offSet);
           }
           out.write(cache, 0, cache.length);
           i++;
           offSet = i * MAX_DECRYPT_BLOCK;
       }
       byte[] decryptedData = out.toByteArray();
       out.close();
       return decryptedData;
   }

   /** *//**
    * <p>
    * 公钥加密
    * </p>
    *
    * @param data 源数据
    * @param publicKey 公钥(BASE64编码)
    * @return
    * @throws Exception
    */
   public static byte[] encryptByPublicKey(byte[] data, String publicKey)
           throws Exception {
       byte[] keyBytes = Base64Util.decode(publicKey);
       X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);
       KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
       Key publicK = keyFactory.generatePublic(x509KeySpec);
       // 对数据加密
       Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
       cipher.init(Cipher.ENCRYPT_MODE, publicK);
       int inputLen = data.length;
       ByteArrayOutputStream out = new ByteArrayOutputStream();
       int offSet = 0;
       byte[] cache;
       int i = 0;
       // 对数据分段加密
       while (inputLen - offSet > 0) {
           if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
               cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
           } else {
               cache = cipher.doFinal(data, offSet, inputLen - offSet);
           }
           out.write(cache, 0, cache.length);
           i++;
           offSet = i * MAX_ENCRYPT_BLOCK;
       }
       byte[] encryptedData = out.toByteArray();
       out.close();
       return encryptedData;
   }

   /** *//**
    * <p>
    * 私钥加密
    * </p>
    *
    * @param data 源数据
    * @param privateKey 私钥(BASE64编码)
    * @return
    * @throws Exception
    */
   public static byte[] encryptByPrivateKey(byte[] data, String privateKey)
           throws Exception {
       byte[] keyBytes = Base64Util.decode(privateKey);
       PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);
       KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);
       Key privateK = keyFactory.generatePrivate(pkcs8KeySpec);
       Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
       cipher.init(Cipher.ENCRYPT_MODE, privateK);
       int inputLen = data.length;
       ByteArrayOutputStream out = new ByteArrayOutputStream();
       int offSet = 0;
       byte[] cache;
       int i = 0;
       // 对数据分段加密
       while (inputLen - offSet > 0) {
           if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
               cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
           } else {
               cache = cipher.doFinal(data, offSet, inputLen - offSet);
           }
           out.write(cache, 0, cache.length);
           i++;
           offSet = i * MAX_ENCRYPT_BLOCK;
       }
       byte[] encryptedData = out.toByteArray();
       out.close();
       return encryptedData;
   }

   /** *//**
    * <p>
    * 获取私钥
    * </p>
    *
    * @param keyMap 密钥对
    * @return
    * @throws Exception
    */
   public static String getPrivateKey(Map<String, Object> keyMap)
           throws Exception {
       Key key = (Key) keyMap.get(PRIVATE_KEY);
       return Base64Util.encode(key.getEncoded());
   }

   /** *//**
    * <p>
    * 获取公钥
    * </p>
    *
    * @param keyMap 密钥对
    * @return
    * @throws Exception
    */
   public static String getPublicKey(Map<String, Object> keyMap)
           throws Exception {
       Key key = (Key) keyMap.get(PUBLIC_KEY);
       return Base64Util.encode(key.getEncoded());
   }

}
